Early end for Dovizioso
Dovizioso, meanwhile, ended his test slightly early after completing a program of 41 laps.
Having led for much of the latter part of the day. 0.041 off the top, the 2017 runner up was overwhelmingly positive about his bike and his bike at Losail - having also completed a longer run on the newer chassis, but there tempering the reaction with positives but some negatives.
Marquez makes headlines
Marquez, who was just 0.167 off Iannone, did make some headlines with a new aero update that was spotted on his Repsol Honda Team machine - as well as a crash.
But the reigning champion was quotable as ever, "Even the crash was good - because we tried the other bike with a different setup."
Pedrosa takes it easy
Marquez' team-mate Dani Pedrosa, meanwhile, took it a little easier on Friday.
After a big crash on Day 1 - he some pain in his hand meaning he didn't push; tenth after 35 laps.
The Spaniard had made big headlines of day 1 when he tumbled twice, though he was declared fit later to ride on the second day.
Not so Rossi!
Movistar Yamaha's Valentino Rossi was P11 and only 0.034 off the top ten and Pedrosa in P10, and the 'Doctor' explained he was having some problems with the front tyre that put paid to a time attack.
But the rider from Tavullia said his pace "wasn't bad", with that front tyre - especially over race distance - a key focus for his side of the garage.
Miller on the move
Alma Pramac Racing were the third Independent Team represented in the top ten and their pairing of Danilo Petrucci and Jack Miller took P8 and P9 to end the day just behind Yamaha's Maverick Vinales.
The two men were split by less than a tenth and it made for another impressive test performance for Queenslander Miller as he settles into life on Ducati machinery - as well as podium challenger 'Petrux'.